2.3 Pollinators’ sampling
Pollinators here mean flower–visiting and nectar–feeding insects. The
transect line was fixed in walking trail of forest, open forest, and
managed habitat, while in the grassland transects were drawn in the edge
and the middle of the grassland with 20 m inter transect distance
(Stanley, 2013).
The survey was performed in the spring and autumn seasons for the
consecutive years 2018 and 2019. In each season, the pollinators were
sampled for 3 consecutive days in sunny weather between 9 am to 4 pm
(Pollard and Yates, 1994). The pollinators were collected by using hand
sweeping and color pans. White, Yellow, and blue color pans were used
for insect sampling. During each sampling day, a transect walk of 30
minutes was done along the 100 m of the trail in the open trail of the
forest, forest trail, and trails of the managed habitat, while in
grassland the transect walk was made in the edge and the middle
(Stanley, 2013). The transect walk method was used to sample butterflies
(Pollard & Yates, 1994), bumblebees (Fussell and Corbet, 1992),
hoverflies, and other bees (Proesmans et al., 2019). During the walk,
insect pollinators that were feeding on flowers within 2m of the
observer were captured, identified, and released (Sutherland, 1996). In
the case of the butterfly, they were observed and identified during
flight and basking within the line transect. Unidentified insect
pollinators were collected in separate vials, transferred in the icebox,
and brought to the lab for identifications.
Similarly, pan traps were deployed in each transect. This method aided
in simultaneous sampling multiple locations, coverage of a large number
of sites, and is the efficient method of bee sampling (Westphal et al.,
2008; Neilsen et al., 2011). The pans were plastic bowls of about 15 cm
diameter and painted with non–toxic three different colors; white,
yellow, and blue (LeBuhn et al., 2003). Each pan was attached to a post
using a metal clamp adjusting bowl the rim. The pan was filled with
about 400ml of detergent water. Three posts were deployed in 100 m
distance and 20m apart from each other. The traps were visited for
collecting the fallen insects after 24 hours and were transferred in
labelled vials with 70% ethanol.